Method of receiving radiosignals with the compound heterodyne



A. HwTAYLOR AND L. 0 YOUNG. METHOD OF RECEIVING RADIOSIGNALS W| TH THE COMPOUND HETERODYNE.

APPLICATION FILED AUG. [2, 1919.

1,414,232; Patented Apr a 25, 1922.

H I away-W61 G in l 7 w [L 92 I I Q Q 6:13am A UNITED STATES PATENT omen,

ALBERT I-IOYT TAYLOR, or GRAND FORKS, NORTH DAKOTA, AND LEo'o. YOUNIGQYOF VAN WERT, OHIO.

METHOD OF RECEIVING RADIOSIGNALS WITH THE COMIEO UND HETERGDYNE.

T aZZwhom it may c ncern.

Be it known that we. ALBERT HOYT TAY- Lon, and LEO C. YOUNG, citizens of the United States, and residents, respectively, of Grand Forks, in the county ofGrand Forks, and, State of North vDakota, and Van \Vert, in the county of Van \Vert and State of Ohio, have invented an Improvecombined with the use of a heterodyne or oscillating circuit whose frequency 15 so chosen that it combines first with the signal to produce an intermediate frequency and 'second with the intermediate frequency to produce audible response,

The present invention differentiates radically from the electric circuits disclosed in the prior art in that it characterized by a single heterodyne which reacts on the incoming wave to produce an intermediate frequency and which intermediate frequency is acted upon a second time by the same heterodyne after having passed through an intermediate tuning circuit. This compound, or

successive operation of the same heterodyne results finally in the production of an audio frequency which is intensified through several stages of amplification and then actuates a signal responsive device. .The reaction of the single heterodyne can be repeated several times in the circuit if desired, there being. theoretically, no limit in the number f stages in the compounding action.

Specification of Letters Patent. Patented Ap 25 1922 Application filed. August 1'2, 1919. Serial No. 317,066.

Our invention 1155' been illustrated, diagrammatically in the accompanying drawing in which A is the antenna which is tuned in the usual manner by means of the variable primary P and variable primary condenser C,, and coupled in the usual manner to a secondary receiving circuit tuned by the condenser C and variable secondary inductance S. Either a crystal detector or bulb may be used with this secondary circuit, which will be called the primary de-1, tector. The drawing shows a three element bulb employed in the usual manner as a pri- 'mary detector D Magnetically coupled'to the secondary S is an oscillating circuit H, containing variable condenser C which is capable of variation over a range of at least double that of the wave lengths to be received. Any arrangement of oscillating bulb may be used for H which is capable of giving the required range of wave lengths.

If the frequency of the incoming signal as and inductance P to the frequency f,

and is loosely coupled to the secondary S, which IS tuned by means of the condenser (h and connected in the usual manner 'with the secondary detector D ;---A certain amount of the frequency passes by wayvof the secondary circuit. S and the amplifiers A, and A and the intermediate loose coupled circuit P and S'to the detector D and here combines with the frequency f, to give an audible signal whose frequency.

f, is equal to f minus The output circuit of D passes to a two stage audio'frequency amplifier, A ,-A which may or may not be necessary, according to the type of receiving collector which is used. The

I trated for a Wave length of 15,000 meters.

f equals 20,000, f equals 10,600, f equals 9,400 cycles and the final audible signal equals 7, minusf equals 1,200 cycles. The

circuit is called the compound 'heterodyne as one heterodyne is made to function two or more times, once on the detector D and its accompanying circuits and then on detectors D D etc- The result of the first action is to 'produce an intermediate frequency, which can be sharply tuned by the intermediate tuning condensers C and C and inductance P and S. The intermediate frequency is usually inaudible when ordinary telephones are used for reception, and when ordlnary ranges of wave lengthsare handled. If it should be desirable .to apply the circuit to an extremely long wave, say 30,000 meters, the. intermediate frequency could be audible, were it not for the use'of the absorbing circuit consisting of the inductance L and capacity C which circuit is placed in parallel with the telephone receivers and tuned to' the intermediate frequency f thereby effectually preventing this frequency from penetrating the telephones. Under ordinary conditions the circuit L and C is not necessary.

The superior selectivity of the circuit may be-demonstrated from the following figures. Taking the same illustration as previously, suppose the circuit is set according to the figures given above for a 15.000 meter wave, that is a frequency of 20,000 per second. If now an interfering wave is produced differing by 2%, it will have a frequency 7", equals 20,400 or 19,600. Let the first case be taken as an illustration. If the adjustments of the set are left correct for 15,000 meters, the interfering wave will have an intermediate frequency of 9.800, so that this interfering wave and intermediate frequency will be 4:02: out of tune. Furthermore, on account of the extremely loose coupling possible in the intermediate circuit, the selectivity is greatly enhanced. It will'be noted that the heterodyne frequency must be close to one half the wave frequency.

The operation of the set in practice is as follows: The primary and secondary having been previously calibrated are set, with a moderately loose coupling. for the wave to be received. The intermediate circuit having been previously calibrated, is set with a fairly tight coupling for a wave length approximately twice as long as the Wave to be received. The amplifiers are adjusted in the usual manner, it being only necessary to burn the bulbs atnormal brilliancy. The heterodyne H is then adjusted in frequency by means of its rotary variable condenser C, until the signal is heard, after which the coupling of the intermediate circuit is loosened and slight adjustments of the tuning condensers C and C are made, if necessary. If then the intermediate frequency should be audible in the telephones as an extremely high pitched note, it is removed by adjusting the tuning condenser C For waves up to 15,000 meters this last is, however, not necessary.

The following observations taken on signals from Nauen, Germany, show the high selectivity of the system. An artificial sig nal was produced so as to have an audibility estimated between 20,000 and 30,000, and differing only 1% from Nauens wave, 12,600 meters. This interfering signal was. received on the compound heterodyne receiving set with an audibility of &0 at the same time that Nauens signals had an audibility of 200. The sameexperiment was made with an e dinary autodyne receiving set. using a very loose coupling, and gave an audibility of for the interferingsignal and 15 for Nauens signal. In other words, the new circuit, according to the audibility measurements, cleared the interference between-fifteen and twenty times better than the standard autodyne circuit. It would have been an easy matter to have continued perfect copy on Nauens signals with a high power American station transmitting at the same time on a wave length differing from Naucns by only 100 meters. whereas this could not have been done with the ordinary autodyne circuit. I

The frequency for the heterodyne is very easily determined from the equation .1. if f2 2 4 and that the intermediate frequency 7', then becomes frgn If it is desirable to get a still higher degree of selectivity'itis possible to n ake the same an audible frequency f,. The heterodyne frequency is then determined by the relation:

. 1 f2 :11 and there will be two intermediate frequencies. Then 21 1 sf. .73- 3 which is the first intermediate frequency. The second intermediate frequency:

To illustrate again at 15,000 meters, that is, if 7", equals 20,000, if the heterodyne be set at 6,333, 7, will be equal to 13,666, which will be the frequency of the first intermediate circuit and 7', will equal 7,333, which is the frequency of the second intermediate circuit, and 1,000 will be equal to the frequency of the final audible signal. Now, this process may, theoretically, be carried on indefinitely leading to a higher and higher degree of selectivity, and on account of the way the amplifiers canbe used, that is to say on the intermediate frequencies, there will be no loss of signal, but rather a gain of signal. It is evident that if the number of intermediate circuits which it is decided to use is N, then thenumber of heterodyne actions which are obtained with the one heterodyne is N+1, and if the final frequency of the audible signal be f, the frequency of the heterodyne will be i e-ff In practiceit has been found that sufficient selectivity can be obtained without using more than two intermediate circuits.

Having thus described our invention what we claim is:

1. The method of selectively receiving radiosignals which consists in combining the incoming oscillations with locally generated oscillations to produce a resultant beat current, rectifying said beat current, combining such rectified beat current with the aforesaid locally generated oscillations to produce a second beat current, and observing the effect of said second beat current.

2. The method of selectively receivin-g undamped radioslgnals whlch consists in com bining the incoming oscillations with locally radiosignals which consists in combining the incoming oscillations with locally generated oscillations to produce a resultant beat cur- 4. The method of selectively receiving radiosignals which consists in combining the incoming oscillations with locally generated oscillations, the frequency difference of such oscillations being such as to produce a beat current of frequency above audibility, rectifying the said inaudible beat curren ombining it with the same locally generated osillations to produce a second beat current of audible frequency, and causing said second beat current to actuate a signal responsive device. a

5. The method ,of selectively receiving radiosigna-ls which consists in combining the incoming oscillations with locally generated oscillations to produce a resultant beat current, passing said resultant beat current through a circuit, resonating saidcircuit to the beat frequency, combining the beat current with the same locally generated oscillations to produce a second beat current,

and Observing the effects of said second beat current.

6. The method of selectively receiving radiosignals which consists in combining the incoming oscillations with locally gen-- erated oscillations i produce a resultant beat current, passing said resultant beat current througha circuit, materially detuning said circuit from the incoming oscillations, combining said resultant beat current with the same locally generated oscillations to produce a second beat current, and observ' ing the effects of the second beat current.

7. The method of selectively receiving radiosignals which consists in combining the incoming oscillations with locally generated oscillations of frequency chosen to produce a beat current of frequency differing from the frequency of the locally generated oscil lations only by an amount within the audible range, passing said locally generated oscillations and said beat current through a circuit, approximately tuning said circuit to the frequencies of both, combining the 10- cally generatedv oscillations with the beat current to produce a second beat current, and observing the effects of the second beat current.

'8. The method of selectively receiving radiosignals which consists in combining the incoming oscillations withlocally generated oscillations to produce a resultant beat cur rent, combining the resultant beat current of beat currents, and observing the effects of one of-said beat currents.

10. The method of selectively receiving radiosignal oscillations which consists in causing a single source of locally generated oscillations to act a plurality of times on 21.

single received signal to produce a plurality of beat currents, selectively amplifying one or more of said beat currents, and observing the effects of one of said heat currents.

11. The method of selectively receiving radiosignal oscillations which consists in causing the same local source of oscillations to act a plurality of times on a single received signal to produce a plurality of beat currents of different frequencies, observing the effects of one of said beat currents, and selectively absorbing disturbing currents.

In testimony whereof we have aflixed our signatures this 26th day of July, 1919.

ALBERT HOYT TAYLOR. LEO C. YOUNG. 

